1. Field of the Invention
The present invention relates to a display device including an inverted staggered thin film transistor in each of a driver circuit and a pixel portion.
2. Description of the Related Art
As one kind of field-effect transistor, a thin film transistor in which a channel formation region is formed using a semiconductor layer formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon, or polycrystalline silicon is used for the semiconductor layer used in the thin film transistor have been disclosed. A typical application of thin film transistors is a liquid crystal television device, in which thin film transistors have been put to practical use as a switching transistor for each pixel that constitutes a display screen.
Further, for reduction in cost of a display device, there is a display device whose number of external components is reduced and in which thin turn transistors formed using amorphous silicon or microcrystalline silicon are used for a gate driver (see Patent Document 1).